Influence of the Pitch-to-Diameter Ratio on Two-Phase Flow-Induced Forces Across a Tube Bundle

Abstract

Flow-induced vibrations of Steam Generator tube bundles are a major concern for the operators and designers of nuclear power plants. In order to predict damages due to such vibrations, predictive calculations are performed, both by designers and by operators, which allow one to evaluate safety margins and thereafter to optimize the SG maintenance policy. In cases when semi analytical models of fluid-dynamic forces are used, together with corresponding dimensionless fluid force coefficients, closures are assessed by experiment. The database of dimensionless coefficients should then cover relevant tube bundle configurations. Within this framework, a test rig which was available at EDF was modified in order to arrange different pitch-to-diameter ratio bundles and different tube diameters. This paper discusses the fluid-induced forces measured on a set of flexible tubes placed in a triangular pitch bundle both in the lift and drag directions. Two-phase flow excitation spectra are presented as well.